The White House has yet to appoint a head of cybersecurity, more than five months after President Obama announced that protecting America's computer systems was a "national security priority".

The slow progress has left some senior figures concerned that government officials are not taking the threat seriously - despite a string of high-profile attacks on America's internet infrastructure.

The role, which is meant to draw together different areas of the nation's cyberdefence for the first time, was announced earlier this year as part of an attempt to coordinate organisations including the National Security Agency, Department of Homeland Security and the Pentagon.

In May, President Obama said that it was vital to establish a White House office responsible for coordinating cybersecurity because it was "one of the most serious economic and national security challenges we face".

"Cyberspace is real, and so is the risk that comes with it," he said at the time. "From now on, our digital infrastructure will be treated as a strategic asset."

It is not yet clear who might be in line to take the White House position, but one frontrunner for the job - former Bush administration adviser Melissa Hathaway - quashed expectations that she would take over when she left her position with the government over the summer.

Hathaway - who oversaw the lightning review that led to the creation of the new, centralised cybersecurity role - resigned in August citing family commitments, and is now working at Harvard.

Last month she said that she was never a serious contender for the top job, and told Federal News Radio that the failure to announce a cybersecurity adviser was not an indication that the job was considered a low priority.

That view was echoed last week by Chris Painter, who took over from Hathaway as the White House's acting senior coordinator for cybersecurity.

"That process is well underway, it's moving forward, and there's not much more I can offer on that," he told a meeting in Washington. "You shouldn't confuse the fact that the person is not in place with the fact that activity is not really going on in the cybersecurity directorate."

However, those comments have yet to satisfy those who believe that the job must be filled sooner rather than later. A number of senior political figures - including former vice presidential candidate Joe Lieberman - have urged officials to fill the vacancy.

"Of course, I'm concerned that we have yet to see that person emerge," said Congresswoman Yvette Clark, who chairs a subcommittee on cybersecurity. "I know the process is underway to identify the individual, the vetting process is one that is very slow and deliberate."